This invention relates to fiber optic technology. More specifically, the invention relates to an apparatus for providing optical interprocessor communication.
A multichip module (MCM) is an electronic package structure consisting of two or more xe2x80x9cbarexe2x80x9d or unpackaged integrated circuits (ICs) interconnected on a common substrate (e.g., a ceramic substrate). The interconnects are usually multiple layers, separated by insulating material, and interconnected by conductive vias. MCMs are known to provide significant performance enhancements over single chip packaging approaches. Advantages of MCMs include a significant reduction in the overall size and weight of the package, which directly translates into reduced system size. Thus, first level advantages include: higher silicon packaging density, short chip-to-chip interconnections and low dielectric constant materials. These advantages lead to the following secondary benefits: increased system speed, increased reliability, reduced weight and volume, reduce power consumption and reduced heat dissipated for the same level of performance.
The ICs can be attached to the common substrate using a flip chip attachment method in which all the input/output (I/O) bumps on an IC are first terminated with a solder material such as a lead/tin high melting temperature alloy. The IC is then flipped over and the solder bumps are aligned and reflowed in a reflow furnace to effect all the I/O connections with the bonding pads on the substrates. A related interconnect technology is C4 (controlled collapse chip connection) which is a method of using a lead-rich lead/tin alloy to mount chips directly to high temperature ceramic substrates. C4 flip chip structures can be built directly over exposed aluminum vias located at the top surface of a wafer.
Computer systems built with multiple MCMs or multiple nodes require the ability for MCMs within the computer system to communicate back and forth. One way to provide high-speed communication of MCM to MCM data is to send the signals electronically. However, the electronic approach can suffer from a lack of scalability in speed due to losses and signal distortion within the printed circuit board that the MCM is attached to, due to electrical connectors, and due to backplane boards that may connect multiple boards containing MCMs. The electrical signal distortion is particularly acute when the boards containing MCMs are on different backplanes. Optical fiber technology has been used as an I/O data interface between computer systems. As processor speeds and densities increase, electrical signaling may not scale with the processor speeds and optical technologies may be required to play a role in: board-to-board (inter-frame) interconnection, card-to-card (intra-frame) communication, module-to-module interconnection, and any combination of these.
One approach to providing high speed optical communication between components (e.g., MCMs) within a computer is to place an optical transceiver on the support printed circuit (PC) board that mounts either single chip modules or a MCM. This approach may not provide speed and scalability because the electrical signal still needs to exit the MCM through the PC card which can limit the speed due to factors such as pin inductance, signal loss in the card, and distortion. It can also consume more power because of the required module drivers and will take up extra space on the PC board.
Another approach to providing high speed optical communication between MCMs is to place the optical transceivers on the MCM within the hermetic seal portion of the MCM. The hermetic seal design should be sufficient to protect the ICs and assist in ensuring chip reliability. The seal typically includes a metal or ceramic casing or cover which encapsulates and seals the MCM to protect against both stray electrical fields and to protect against environmental factors such as water vapor and gases. Placing the optical transceivers on the MCM within the hermetic seal solves the electrical problems associated with the first approach, but requires the development of a new method of exiting fiber optics through the seal or including an optical connector within the seal. This could present a difficult technical and manufacturing problem and may compromise the integrity of the seal.
An exemplary embodiment of the present invention is an apparatus for providing optical interprocessor communication. The apparatus comprises a multichip module and an optical module. The multichip module includes a substrate, an integrated circuit electrically connected to the substrate and a hermetically sealed cover. The hermetically sealed cover encloses a sealed portion of the substrate and the integrated circuit is inside of the sealed cover. The optical module includes an optical transceiver located on the substrate outside of the sealed portion and the optical transceiver is electrically connected to the integrated circuit through the substrate. An additional embodiment includes a system for providing interprocessor communication.